Current mode switching converters are usually characterized by two control feedback loops, one for controlling the regulated output voltage and the other for controlling the output current. Current mode switching converters include those that sense and control peak current through an inductor, which gives rise to serious problems, including poor noise immunity, a need for slope compensation, and peak-to-average errors which the inherently low current loop gain cannot correct. Average current mode control eliminates these problems, or at least minimizes them. Average inductor current mode switching converters regulate the averaged current through the inductor to provide excellent inductor current regulation and noise immunity. Such switching converters also may be used effectively to control current other than inductor current, allowing a much broader range of topological applications.
A major drawback to average current mode regulation is that recovery can be slow from a step in the desired regulation current, usually encountered for example when going from a no load condition to a load condition. During a step response, the regulator must gradually slew the inductor current to its final regulated level. This is in contrast to a peak current-mode converter that will charge the inductor at nearly 100% duty-cycle until the desired peak inductor current level is achieved.